This invention relates to an assembly for opening and closing a gate vertically rotatable about an axle. More particularly, the invention relates to a counterbalancing assembly used to counterbalance the weight of the gate.
With vertically rotatable gates, it is common to provide a counterbalancing assembly to counter the weight of the gate as the gate is rotated about its axle. If the counterbalancing assembly is not provided, it is difficult to open the gate. Previously, these counterbalancing assemblies have used weights to counterbalance the weight of the gate. These weights are mounted to the gate on the side of the axle opposite the gate. These weight driven assemblies are illustrated by U.S. Pat. No. 1,611,367 to Pickett.
It also has been recognized that when the center of gravity of the gate moves to the other side of the axle, the gate falls under the influence of gravity. In these weight driven systems, a spring was often used to cushion the fall. See U.S. Pat. No. 1,257,333 to Fawick.
An improvement on the weight driven counterbalance systems was provided in U.S. Pat. No. 1,386,113 to Houck. In the Houck patent, a cable is attached to the axle-end of the gate and to a weight which is suspended from one end thereof. The cable and weight assembly is used to counterbalance the weight of the gate both when the gate is in the closed position and when the gate is in the opened position. However, with this device, the use of a suspended weight can be a safety hazard and, secondly, there must be a super structure for supporting weight which will provide enough clearance so that the weight will not hit the ground before the gate rotates completely.
An improvement over the weight driven systems is illustrated in U.S. Pat. No. 3,839,826 to Reis which illustrates in FIG. 4 a spring operated counterbalance system. In this patent, a coil spring assists in opening the vertically rotatable gate and, as the gate opens, it begins to load a separate torsion spring. Here the torsion spring cushions the gate as it falls to the open position and further assists in closing the gate once it has been opened.
Another spring counterbalancing device is shown in U.S. Pat. No. 4,481,737 to Rebhan. In this device, a coil spring assists in opening the gate and a second coil spring is placed in tension as the gate is opened. This second spring assists in closing the gate once it is opened.
In the above two patents, where springs were used instead of weights to provide a counterbalancing force, it was necessary to provide two springs to counterbalance the weight of the gate - one spring was used to counteract the weight of the gate when the gate was being opened and the second spring was used to counteract the weight of the gate when it was being closed.
U.S. Pat. Nos. 4,381,626; 4,270,221; and 4,270,312 to Courtis all show a vertically rotatable gate in which a single spring is used to provide a counterbalance force effective in both the closed and opened gate positions. The Courtis patents describe a single counterbalancing spring which is caught in its mid-portion by an arcuate spring-engaging fulcrum as the gate is being opened. Thus, a single spring provides a counterbalancing force in two directions; the particular direction being determined by the position of the gate. However, because the spring is being stretched arcuately over the fulcrum, the spring grinds against the fulcrum providing a "noisy" mechanism. Further, this grinding may be abrasive to the springs causing deterioration of the springs over time.
There have been developments with vertically rotatable gate counterbalancing assemblies over the years, however, a needs exists to have a simple, compact but effective, spring-type counterbalance assembly which is not subject to deterioration as previously known.